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Comments

You can write text that the program will ignore by beginning the line with a #, this helps with reminding you what certain code does or for explaining purposes.

# This is a comment

Data Types

Variables can store data of different types, and different types can do different things.

Python has the following data types built-in by default, in these categories:
Text Type: str
Numeric Types: int, float, complex
Sequence Types: list, tuple, range
Mapping Type: dict
Set Types: set, frozenset
Boolean Type: bool
Binary Types: bytes, bytearray, memoryview

We will go more in-depth on some of these types in the next few paragraphs.

You can print the data type of a variable with the type() function:
x = 5
print(type(x))

Strings

Strings are surrounded by either single quotation marks, or double quotation marks.

You can assign a multiline string to a variable by using three quotes:
x = """The FitnessGram Pacer test is a multistage aerobic capacity test that progressively gets more difficult as it continues. The 20 meter Pacer test will begin in 30 seconds."""

You can check the length of a string using the len() function: x = "hello"
print(len(text)) # returns 5


Numbers

There are 2 primary, int and float

x = 2 # int
y = 2.8 # float

To verify the type of an object in Python, use the type() function: print(type(x))
print(type(y))

Int, or integers, are whole numbers, positive or negative, without decimals.

Float is a number, positive or negative, containing one or more decimals.

Both strings and numbers are built-in data types.

Strings

A string is a sequence of characters representing text. Strings are typically enclosed in quotation marks and can be stored in variables for later use in a program.

#include <ostream>
#include <string>


int main()
{
// Declare a string variable
std::string str = "codinghome";
}

Integers and Floating Point Numbers

Simply said, Integers are used for numbers without a decimal, and Float is used for numbers with decimals, simply said. There is more to that but we are keeping it simple.

#include <iostream>

int main() { // Declare an integer variable int num = 10; // Declare a floating-point variable float fnum = 10.5; }

Print

Printing an output to the terminal/console or whatever you want to call it.

#include <iostream> int main() {   // Declare an integer variable   int num = 10;   // Declare a floating-point variable   float fnum = 10.5;   std::cout << "num: " << num << std::endl; // <-- Prints the integer Variable (Variable num)   std::cout << "fnum: " << fnum << std::endl; // <-- Prints the floating point Variable(Variable fnum) }

Data Types

In Haskell, types are how you describe the data your program will work with. Types can be simple, like:

• Bool: boolean True or False.
• Char: one character.
• Int: fixed-precision signed integer (usually 64-bit)
• Float / Double: floating-point values.

Or, they can be composed with constructs, like:

• String: shortcut for [Char].
• [a] : list of as (where a is a general type).
• (a, b) : tuple composed of a and b
• Just a : Maybe monad with the Just option

Function Type Declaration

Haskell's functions will usually have 2 parts: a type declaration, and the implementation of the function itself (the type part can also be inferred):

• Bool: boolean True or False.
• Char: one character.
• Int: fixed-precision signed integer (usually 64-bit)
• Float / Double: floating-point values.

Notice the type declaration has 2 types of "arrows": => and ->.

• => : used for giving additional context of what rules a should follow (in the example above, we see a should be part of the Eq class, which allows for comparison)
• -> : used for actually declaring the type of the function (in the above example, we see the first argument is a, a general, comparable type, then a list of as and then finally it outputs an Integer)

Function Definition

Functions are defined like: functionName argument(s) = expression. Haskell forces declarative style, so functions are (usually) composed of just an expression (always returns a value).

Functional Principles

Haskell restricts to the functional paradigm, meaning Haskell enforces:

• Immutability: when the data has to be defined again for it to "change"
• Purity: functions must be pure, producing no side-effects (like modifying a global variable), and must be deterministic (f(x) = y, no matter when f is called)
• Higher-order functions: functions must be first-class, meaning they can be passed as arguments to other functions. This allows for higher-order functions. which take a function and other data and apply the function to the data in different ways.
• Disciplined state trying to minimize the use of mutable state and trying to make it local when possible.

Comments

In-line comments are made with -- and block comments with {- -}:

Example Document

The <!DOCTYPE> declaration represents the document type, and helps browsers to display web pages correctly. It must only appear once, at the top of the page (before any HTML tags). The <!DOCTYPE> declaration is not case sensitive.

HTML Headings

HTML headings are defined with the <h1> to <h6> tags. <h1>defines the most important heading. <h6> defines the least important heading:
<h1>Big</h1>
<h6>Small</h6>

HTML Paragraphs

HTML paragraphs are defined with the <p> tag:
<p>This is a paragraph.</p>
<p>This is another paragraph.</p>

HTML Links

HTML links are defined with the <a> tag:
<a href="https://example.com">This is a link</a>

HTML Images

HTML images are defined with the <img> tag. The source file (src), alternative text (alt), width, and height are provided as attributes:
<img src="example.jpg" alt="example.com" width="104" height="142">

Example Document

h1 {
  color: black;
  text-align: center;
  font-size: 26px;
  font-family: verdana;
}

<p style="font-size:10px">

To put CSS files in HTML, use:
<link rel="stylesheet" href="style.css">

To put CSS code in HTML, use:
<style>
.class {
}
</style>

CSS Rulesets

Properties - With these, you can style a HTML element, like for example; color.
Property Value - This chooses one of the possible options for a given property, like red for color.

You can also write CSS like html{color:red;}
You can also put styles in HTML elements. <h1 style="font-color:white;">
You can also select multiple elements at once like...
h1, h4, h6, h2 {   color: red; }

Classes

Think of classes like custom HTML elements, they can be applied in html like <p class="text-red">

Classes begin with a dot or period (.) to begin the selector.

.text-red {   color: red; }

Text Elements

font-size: 10px; - Text size, can be in pixels.
font-family: verdana; - Fonts
text-align: center; - Can align to the left side, right side, or in the center of the webpage.
text-shadow: 3px black - Shadow of text. It can be in pixels and colors.

Padding Elements

padding-top: 50px; - Separation. It can be top, left, right, and bottom in pixels.
margin: 50px; - A margin. It can be in pixels.
border-width: 5px; - Border width. Can be thin, medium, thick, or just pixels.
border-style: dotted; - Border style. Can be dotted, dashed, solid, double, groove, ridge, inset, outset, none, or hidden. Can also be colored.
width=500px; - Width of the element. It can be pixels or percentages.

Color Elements

color: red; - The color of the element, can be hexadecimal, or RGB.
background-color: white; - Background color of the element.

Comments

Comments are commonly used to explain the code and may help when you edit the source code later and are ignored by browsers.

A CSS comment starts with /* and ends with */, and no changes are needed to make it multiple lines.

/* This is a single-line comment */

/* This is
a multi-line
comment */

Extra: Centering Images

img {   margin: 0 auto;   display: block; }

Including JavaScript in an HTML Page

<script type="text/javascript">
//JS code goes here
</script>

Call an External JavaScript File

<script src="myscript.js"></script>

Including Comments

Single line comments - // Comment
Multi-line comments - /* comment here */

Variables

var, const, let
var — The most common variable. It can be reassigned but only accessed within a function. Variables defined with var move to the top when code is executed.
const — Can not be reassigned and not accessible before they appear within the code.
let — Similar to const, however, let variable can be reassigned but not re-declared.

Data Types

Numbers — var age = 23
Variables — var x
Text (strings) — var a = "init"
Operations — var b = 1 + 2 + 3
True or false statements — var c = true
Constant numbers — const PI = 3.14
Constant numbers — const PI = 3.14
Objects — var name = {firstName: "John", lastName: "Doe"}

Objects Example

var person = {
  firstName: "John",
  lastName: "Doe",
  age: 20,
  nationality: "American"
}
  

Querying Data from a Table

Query Data in Columns c1, c2 from a Table

Query All Rows and Columns from a Table

Query Data and Filter Rows with a Condition

Query Distinct Rows from a Table

Sort the Result Set in Ascending or Descending Order

Skip Offset of Rows and Return the Next n Rows

Group Rows using an Aggregate Function

Filter Groups using Having Clause

Modifying Data

Insert One Row into a Table

Insert Multiple Rows into a Table

Insert Rows from t2 into t1

Update New Value in the Column c1 for All Rows

Update Values in the Column c1, c2 that Match the Condition

Delete All Data in a Table

Delete Subset of Rows in a Table

Table Management

Create a new Table with Three Columns

Delete the Table from the Database

Add a new Column to the Table

Drop Column c from the Table

Add a Constraint

Drop a Constraint

Rename a Table from t1 to t2

Rename Column c1 to c2

Remove all Data in a Table

Example Document

All JSON files are surrounded by { and }, which means it is a object. Unlike Javascript, you must use double quotes (") for strings, not singular quotes (')

Importing JSON